Bleaching cotton textile goods



FIFSSOL QR Patented Aug. 19, 1947 BLEACHING COTTON TEXTILE GOODS Donald J. Campbell, Niagara Falls, N. Y., assignor to E. I. "du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application September 1, 1943,

! Serial No. 500,839

5 Claims.

This invention relates to a new and improved process by which textile fabrics, particularly cotton, are given a preliminary treatment prior to bleaching in order that more effective action and more efiicient results may be secured during the bleaching. More especially, it relates to a new and improved process for treating cotton piece goods prior to bleaching utilizing a peracid in the treatment whereby the absorbency and whiteness of the textile fabric are considerably improved.

In the preparation of cotton textile fabrics for bleaching it is now usual to subject the fabrics to a preliminary acid sour utilizing as the acid an inorganic acid, generally sulfuric acid. This preliminary treatment of the textile, when followed by treatment with caustic and bleaching, or simply by bleaching alone, has the effect of improving the absorbency of the goods as well as the whiteness of the textile fabric at the conclusion of the bleaching step. I have now found that when in place of an inorganic acid such as sulfuric acid there is utilized a peracid, either persulfuric acid or an organic peracid, the absorbency and whiteness of the treated fabric are very much improved. The peracids appear to act on non-cellulosic impurities occurring in the cotton, an effect not obtainable with the presently-utilized acid sours, whereby these impurities are rendered more readily soluble in alkaline solutions. As a result various impurities present in or on the cotton are solubilized and removed and, at the conclusion of the bleaching operation, the textile fabric is characterized by superior whiteness and improved porosity.

Accordingly, it is one of the objects of my invention to render available a method to be employed prior to bleaching of cotton textile fabrics whereby the absorbency and whiteness of the resulting bleached textile fabrics are much improved. Another object of my invention is to provide a method by which cotton may be preliminarily treated with a peracid, either an inorganic peracid or an organic peracid such as an organic monoperacid, whereby natural impurities present in or on the cotton may be solubilized and removed. These and still other objects of my invention will be apparent from the ensuing disclosure of certain preferred embodiments thereof.

In carrying out my improved process I first prepare an aqueous solution of a peracid. Among suitable peracids very satisfactory results have been secured with persulfuric acid, peracetic acid, monoperphthalic acid, and monopersuccinic acid, although any of the organic peracids produced, for example, in accordance with the Reichert et al. Patent No. 2,284,477 may be utilized.

The concentration of peracid in the aqueous treatment bath may vary over considerable limits, percentages ranging from 0.5% to 20% by weight being especially satisfactory. I have obtained very good results with an aqueous solution of a peracid of approximately 2% concentration.

ranging from room temperature to a temperatureof 200 F. or higher. At elevated temperatures the time of treatment must be carefully controlled in order to avoid the oxidation of the cotton to oxy-celluloses with resulting degradation of the textile fabric.

The time required for the treatment will naturally depend upon the concentration of peracid, but I have found that periods ranging from 15 minutes to over-night treatments of twenty hours or longer are especially satisfactory. The ouring step, involving immersion in the aqueous solution of the peracid, may be the first step of the bleaching process, or the goods to be treated may be first given a desizing treatment of any usual type such, for example, as in an' aqueous bath containing an enzyme preparation such as Rapidase.

Subsequent to the peracid souring step the goods may be directly bleached, or they may be given a caustic pre-treatment in accordance with the usual practice now employed in peroxide bleaching. This caustic treatment may follow the procedure described in the Campbell et a1. Patent No. 2,267,718, which procedure may also be followed during the bleaching step, although bleaching by any usual peroxide treatment method such as kier bleaching may be utilized. Ordinarily I prefer at the conclusion of the peracid sour to treat the goods with a caustic soda solution, either in a simple caustic immersion step, or by following the procedure described in Patent 2,267,718. At the conclusion of this caustic treatment the goods are preferably bleached with hydrogen peroxide or sodium peroxide by means of the so-called continuous bleach method as described, for example, in Patent 2,267,718 and in the co-pending application of Campbell and Fennell, Serial No. 354,866, filed August 30, 1940, now Patent No. 2,334,066. As previously stated, however, my souring step utilizing a peracid may be followed by any method of bleaching involving the use of peroxygen compounds, which bleaching step may either follow the sour directly, or, as an alternative, it may follow an intermediate caustic treatment step.

My improved souring step utilizing a peracid such as an organic peracid or organic monoperacid, or an inorganic peracid such as persulfuric acid,.is far superior to the usual souring operation insofar as improving the absorbency and whiteness of the textile goods is concerned. This is illustrated by the comparative determinations tabulated below, showing the percentage whitenesses as measured with the Bleachometer of samples of the same cotton piece goods treated with the usual souring agent, sulfuric acid, as compared with souring by means of our improved souring agents, persulfuric acid and peracetic acid, these being taken as typical of these agents. These whitenesses are determined in accordance with the usual practice after ironing, and the length of the souring step ranged from fifteen minutes to twenty hours with each agent, as indicated in the table. The table gives the percentage whitenesses at the conclusion of the souring step, at the conclusion of a succeeding operation wherein the cotton piece goods were subjected to a caustic boil treatment in a 1% caustic soda solution for thirty minutes, and at the conclusion of the subsequent bleaching step wherein the goods were treated, in accordance: with the procedure described in Patent 2,267,718, with a solution comprising hydrogen peroxide of 0.125 volume concentration, and six lbs. of 42 Baum sodium silicate per 100 gallons of bleach liquor. The bleaching treatment was for one hour at 180 F.

TABLE I Per Cent Whiteness Persul- Pera- Sulfuric Length rifii Add $333 E5553 Sour Sour Sour SonringStep:

15 min 72. 2 72.2 74.1 1 ht. 72. 5 74.0 76. 2 4 hrs 71. 9 75.1 77. l 20 hrs 71. 77. 80. 6

1% NaOH, 30 MIN.

After N aOH Boil:

15 min 75. 2 76. 3 76.9 1 hr Boil with l caustic 74. 5 76. 9 77.8 4 hrs soda solution. 74. 8 7'9. 5 79. l 20 hrs.. 76. 3 8i). 5 81. 8

0.125 Vol. hydrogen peroxide solution containing 6 lbs. of 42 B. sodium silicate. Treatment one hour at 180 F. per 100 gallons of bleach liquor.

AftelrfiBleach: 81 0 85 9 8 g min... 5. 1 hr Bleached 80.9 at. 5 86. 4

drogen peroxide as 4 hrs.--" described 81. 0 89.1 86. 2 20 hrs s2. 4 9o. 2 89.3

It will be noted that increase in the duration of the souring period when sulfuric acid is used as the souring agent from fifteen minutes to twenty hours has apparently no efiect in increasing the percentage whiteness as determined at the conclusion of the souring step, after the caustic soda boil, or after bleaching. As contrasted with this when persulfuric acid and peracetic acid, typical of the peracids that I utilize, are employed as the souring agents an increase in the time of treatment results in very significant increases in percentage whitenesses, as determined at all points in the process, i. e. at the conclusion of the peracid sour, after the caustic soda boil, and after bleaching.

The effect of peracid souring agents in improving the absorbency of cotton textile goods, as contrasted with .the usual souring step employing sulfuric acid, is shown in Table II. The absorbencies were determined by the drop method, involving placing a few drops of Water on the textile fabric and determinin the time necessary for the water to be absorbed. This is a good indication of the ability of the treated fabrics to absorb dyestuffs. In some cases, as will be evident from the following table, the goods possessed practically no absorbency even when the water was allowed to stand thereon for long periods of time. This condition is termed water repellent, and is indicated by the letter R in the following table. In certain other cases the water was not absorbed in two minutes, indicating goods of a low order of absorbency, marked by the letter L in the table. In all other cases the value given for absorbency is the number of seconds of time required for the water to be absorbed by the cloth, and it is evident that the lower these values the greater is the degree of absorbency of the cloth.

In all cases in the following table the absorbency was determined both before ironing and after ironing. It will be noted that ironing tends to lessen the absorption properties, but in the standard determination of absorbency the goods are usually first ironed to provide a more even surface and to simulate the effect of drying the material on heated cylinders.

TABLE II Absorbencies Sulfuric Acid Persulfuric Acid Peracetic Acid souring Agent Soul-mg Agent Souring Agent Length of Subsequent Treatment after Sourmg Before After Before After Before After Ironing Ironing Ironing Ironing Ironing Ironing Sour:

15 min iii: none R: 20 R. AfterlNaOH l5 mi.n R g k sec R. it; :3 Caustic Soda B011 5:331: R::::::: L::::::: 28223:: 3 20 hiIIII L L 30sec 5sec- L. After Bl ach:

15 min. L R 12 sec 60sec.-. 8sec L. 1 hr Bleached with hydrogen per- L R 12 sec 20 sec. 6 sec L. 1 hr oxide as described L R 5 sec 7 sec 2 sec 120 sec. 20 hr sec--- L 2sec 4sec. lsec 5sec.

QEMIUH m1 These data show that better absorbency results when persulfuric acid and peracetic acid are utilized as the souring agents, as compared with the usual souring agent, sulfuric acid. The improvement in absorbency is especially noticeable after caustic boil and bleaching treatments. Persulfuric acid and peracetic acid are taken as typical of the peracids utilized in my souring step, and substantially similar results would be obtained by the use of any other peracids such as monoperphthalic acid monopersuccinc acid, monoperbenzoic, monopermaleic, or any of the other peracids described or prepared in accordance with Reichert et a1. Patent, 2,284,477.

As examples of my new and improved process the following may be given:

EXAMPLE 1 Persulfuric acid was prepared by adding eighty parts by weight of fuming sulfuric acid to twenty parts by weight of cold loo-volume hydrogen peroxide solution. The volume concentration of a solution of a peroxygen compound (such as hydrogen peroxide) is the number of volumes of oxygen gas that would be evolved at 25 C. upon complete decomposition from one volume of the solution, the oxygen gas being measured at 760 millimeters of mercury pressure and at C. The commercial solution of hydrogen peroxide sold under the trade-mark Albone is of 100-volume concentration and contains approximately 27.6% hydrogen peroxide.

The fuming sulfuric acid was added drop by drop from a burette to the hydrogen peroxide solution, during which time the liquid was immersed in an ice bath. In this way decomposition and loss of active oxygen during preparation of the persulfuric acid was avoided.

The cotton textile goods to be treated were then given a desizing operation utilizing a procedure frequently employed in the textile industry employing a 3% solution of Rapidase enzyme preparation at 165 F. The goodswere allowed to remain in contact with the solution of the enzyme for one hour, whereupon they were washed in hot water.

From the persulfuric acid solution previously prepared enough was added to distilled water to provide a solution of 2.5% concentration. The desized cotton piece goods were then wet with this solution in such a way as to have approximately 100% liquid concentration, i. e. the weight of persulfuric acid solution absorbed was approximately equal to the dry weight of the goods. The wetted goods were then stored for various periods of time ranging from fifteen minutes to twenty hours, whereupon they were washed and prepared for subsequent caustic treatment and bleaching operations.

The caustic boil was carried out using a solution of sodium hydroxide of 1% concentration for a period of thirty minutes. The bleaching was carried out by the continuous bleach method as described in the Campbell and Fennell Patent No. 2,267,718, the bath of hydrogen peroxide solution being of 0.125 volume concentration. The bath was rendered alkaline by the addition of 42 B. sodium silicate in amount equivalent to six pounds of the silicate per 100 gallons of bleach liquor. The storage of the goods in the J-box, in accordance with the method described in the aforesaid patent, was for one hour at a temperature of substantially 180 F.

Cotton goods bleached in this way were found to be of superior whiteness and improved absorbency. The whiteness obtained was much higher, utilizing the same amount of hydrogen peroxide solution and caustic soda, than could be obtained by following the usual preliminary souring step wherein sulfuric acid is utilized as the souring agent.

EXAMPLE 2 A peracetic acid souring bath having an avail able oxygen content equivalent approximately to that of the persulfuric acid bath of Example 1 was prepared by reacting a solution of sodium peroxide equivalent in concentration to 3.6 grams of peroxide per liter with a solution of acetic anhydride containing 4.35 cubic centimeters of acetic anhydride per liter. This resulted in a solution of peracetic acid of 0.5 volume concentration, and its pH value was adjusted to approximately 4.5 by the addition thereto of the required amount of sulfuric acid.

The cotton textile goods were first desized as in Example 1 utilizing a 5% solution of Rapidase, the treatment period being one hour at 165 F. They were then immersed in the solution of peracetic acid for various periods of time. The liquid content of the textile goods was so controlled that they contained approximately of the souring liquor, i. e. an amount equal to the weight of the cotton, and the storage periods in the peracetic acid solution ranged from 15 minutes to twenty hours. At the end of this treatment period the cotton goods were washed and subjected to subsequent caustic boil and peroxide bleach steps, following th procedure described in Example 1.

At the conclusion of the treatment the cotton piece goods were found to be of superior whiteness and improved absorbency, the whiteness, for equivalent amounts of hydrogen peroxide utilized in the bleaching step, being considerably greater when peracetic acid was used as the preliminary sour than when the usual sulfuric acid sour was employed.

As various changes may be made in my preferred procedure described herein as illustrative of my process which will nevertheless be within the scope of the invention, it is intended that such Variations shall be included within the scope of the appended claims.

Iclaim:

1. In a process for bleaching cotton textile goods in which the goods are subjected successively to desizing, souring, and bleaching treatments, carrying out the souring step by subjecting the goods to treatment with an aqueous solution containing 0.5% to 20% by weight of a peracid taken from the group consisting of persulfuric acid, peracetic acid, monoperbenzoic acid, monoperphthalic acid, and monopersuccinic acid, and then bleaching said cotton textile goods with an aqueous alkaline solution of a peroxygen compound taken from the group consisting of hydrogen peroxide and sodium peroxide.

2. In a process for bleaching cotton textile goods in which the goods are subjected successively to desizing, souring, and bleaching treatments, carrying out the souring step by subjecting the goods to treatment with an aqueou solution containing 0.5% to 20% by weight of peracetic acid, and then bleaching said cotton textile goods with an aqueous alkaline solution of a peroxygen compound taken from the group consisting of hydrogen peroxide and sodium peroxide.

3. In a process for bleaching cotton textile goods in which the goods are subjected successively to desizing, souring, and bleaching treatments, carrying out the sourin step by subjecting the goods to treatment with an aqueous solution containing 0.5% to 20% by weight of monoperbenzoic acid, and then bleaching said cotton textile goods with an aqueous alkaline solution of a peroxygen compound taken from the group consisting of hydrogen peroxide and sodium peroxide.

4. In a process for bleaching cotton textile goods in which the goods are subjected successively to desizing, souring, and bleaching treatments, carrying out the souring step by subjecting the goods to treatment with an aqueous solution containing 0.5% to 20% by weight of persulfuric acid, and then bleaching said cotton textile goods with an aqueous alkaline solution of a peroxygen compound taken from the group consisting of hydrogen peroxide and sodium peroxide.

5. In a process for bleaching cotton textile goods in which the goods are subjected successively to desizing, souring, and bleaching treatments, carrying out the souring step by subjecting the goods to treatment with an aqueous solution containing 0.5% to 20% by weight of a peracid taken from a group consisting of persulfuric acid, peracetic acid, monoperbenzoic acid, monoperphthalic acid, and monopersuccinic acid, subjecting said goods to treatment with a caustic soda solution, and then bleaching said cotton textile goods with an aqueous alkaline solution of a peroxygen compound taken from the group consisting of hydrogen peroxide and sodium peroxide.

DONALD J. CAMPBELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,110,649 Franz Mar. 8, 1938 2,304,435 Bell Dec. 8, 1942 1,106,107 Parish Aug, 4, 1914 1,767,543 McKee June 24, 1930 1,750,657 Adolph Mar, 18, 1930 57,649 Du Motay Aug. 28, 1866 1,034,658 Steiger Aug. 6, 1912 1,075,663 Meerbott Oct. 14, 1913 2,145,062 Taylor Jan. 24, 1939 2,283,141 Kauflman May 12, 1942 2,173,040 Muller Sept. 12, 1939 1,087,584 Hirschberger Feb. 17, 1914 2,253,242 Mac Mahon Aug. 19, 1941 FOREIGN PATENTS Number Country Date 784,828 France July 25, 1935 798,566 France May 20, 1936 692,981 France Nov, 13, 1930 394,989 Great Britain June 27, 1933 479,965 Great Britain Feb. 15, 1938 203,282 Germany Oct. 20, 1908 5 Claims. (Cl. 8-111) Certificate of Correction Patent No 2,426,142. August 19, 1947.

DONALD J. CAMPBELL It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 3, Table I, under the headin Subsequent Treatment, second portion thereof, for Boil with 1- caustic soda so ution read Boil with 1% caustic soda solution; Table II, first column thereof, next to the last line, under the heading Length of, for 1 hr read 4 hr and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice. Signed and sealed this 24th day of February, A. D. 1948.

THOMAS F. MURPHY,

Assistant Oommz'ssioner of Patents. 

